Bag filling machines have been used for many years to avoid the high labor costs in bagging flowable material. In the bagging of powdery material such as flour, the first bags used were burlap or cotton bags. These were permeable to air and hence as the bags were filled air could escape through the pores and of course some of the flour also escaped through the pores. A standard method of filling powdery material into such bags was by the method of filling from the bottom up. A long spout was used and the bag was raised over the entire length of the spout so that the bottom of the spout was near the bottom of the bag. Then as the bag was filled, the bag was lowered more or less in unison with the filling theoretically to fill the bag from the bottom up without much aeration of the powdery material during filling. The industry more recently has gone away from cloth bags to paper kraft bags which are less permeable to air passage but still somewhat permeable. Even more recently barrier bags have been used and these are the type with a plastic liner within the kraft paper outer bag. Such plastic liner does not let the air escape during filling so that it has been difficult to fill bags with powdery material such as powered milk. Another problem is that with powered milk or flour, strict sanitary precautions must be observed. With many prior bag filling machines using a barrier bag, after the plastic liner was filled on the machine, a man had to separately twist together the top of the plastic bag, put a twist tie on it and then tuck this fastened top of the plastic liner down inside the kraft bag. The man's hands would touch the inside of the bag and therefore this was not particularly sanitary. Also it took about four or five men to operate such a bag machine, yet only about two to four 50-pound bags could be filled per minute. One reason for the slow filling procedure was because the 50-pound slug of powdered material would drop through the air and become aerated, and it took time for the air to escape. A certain amount of time had to elapse after the bag was filled to allow the powdered material to settle before the bag could be closed. This limited the productivity of the men and machine.
In some cases with the old machines a sufficient volume of air becomes entrained in the powdery material so that the bag did not have sufficient capacity to initially contain the 50-pound slug of material and the bag would overflow.
Another problem with the prior art bag machine filling systems was that in many cases a 50 thousand pound storage bin was filled so full that the powdery material could not be de-aerated until the level of the powdery material in the bin had dropped to perhaps one quarter full. This is because there was so much weight of material on the material at the bottom that the air could not escape. As a result the material augered from the bottom of this large bin into the funnel shaped bag filling station in the machine would definitely be aerated and hence was aerated as it went into the bags. This aeration was further caused by the dropping from the auger into the funnel which would re-aerate the powdery material even if it was de-aerated at the large storage bin.
Accordingly the problem to be solved is how to increase the productivity of a bag machine and how to prevent as much aeration as possible and also to de-aerate the powdery material before and during the time that it goes into the bags.